Trench cutting machines are used in a wide variety of environments and for a wide variety of purposes. One such environment is soft dirt or clay, such as is frequently encountered in digging trenches for water lines or sewers or electrical lines which are buried a relatively short distance below the earth's surface in a soft dirt or clay. In other environments, trenches must be cut in medium hard rock formations (that is, formations having a compressive strength on the order of 6,000 - 12,000 psi, such as limestone and sandstone) and in extremely hard rock formations (that is, formations having a compression strength of 25,000 psi minimum, such as diorite, granite, quartzite, or basalt).
The prior art has provided a variety of machines for cutting trenches. Certain of these prior art devices are shown in U.S. Pat. Nos. 3,219,390, 3,374,034, 3,472,555 and 3,148,917.
The present invention departs from these and other prior art trench cutting machines by providing a hard rock trench cutting machine which is particularly well suited for use in underground mining when medium hard to extremely hard earth formations are encountered. In such mining, a vein of coal or ore which is mined may be of insufficient height to permit a mining railroad car to travel through the space which is left after the vein is mined. The hard rock trench cutting machine according to the present invention is used to cut a trench through the hard rock at the bottom of the vein to provide a trench of sufficient depth to permit a mining railroad car to travel in the trench to permit removal of coal or ore from more remote locations in the vein.
The present invention accomplishes this by providing a hard rock trench cutting machine which includes a main body assembly, a cutter wheel assembly, and a longitudinal thrust assembly.
The main body assembly includes two longitudinally extending support booms, each having a forward portion and a rearward portion. Two pairs of laterally opposed side wall support feet on the rearward portion of the booms move laterally outwardly relative to the booms and push against the trench side walls with a force sufficient to secure the booms against longitudinally movement relative to the side walls. The forward portions of the booms are connected to one another by a removable yoke.
The cutter wheel assembly includes a cutter wheel frame slidably carried by the forward portions of the support booms. The cutter wheel frame includes a cutter wheel drum rotatably carried by the cutter wheel frame for rotation about a predetermined axis. The cutter wheel drum carries a plurality of roller cutters for engaging the end face of the trench. A rotational drive means rotates the cutter wheel drum relative to the cutter wheel support frame.
The longitudinal thrust assembly includes two double acting hydraulic cylinders. Each of the cylinders has one end connected to the main body assembly and another end connected to the cutter wheel frame of the cutter wheel assembly. During cutting of the trench, the cutter wheel drum is rotated and the double acting cylinders extend to push the cutter wheel frame longitudinally along the booms. When the cutter wheel frame reaches the forward end of the booms, the cutter wheel drum is stopped and the support feet on the main body assembly are retracted. The hydraulic cylinders are then retracted to pull the main body assembly forwardly to the cutter wheel assembly. The support feet of the main body assembly are then extended to start another cycle of the machine.